The regeneration of pancreatic islet mass in type 1 diabetes may be achievable through recapitulation of islet ontogeny, activation of islet neogenesis or by genetic engineering of non-beta cells to adopt a beta-cell phenotype. Such approaches would overcome the limitations to islet transplantation imposed by paucity of donor tissue and provide a cure for all affected individual. Much remains to be learned about the development of the islet at the molecular level before such therapies become a reality, most notably in the area of the spatio-temporal regulation of transactivators, growth factors and cell adhesion molecules. The current proposal aims to test the general hypotheses that peptides secreted by the developing endocrine cells contribute to the growth and differentiation of the tissue in both an autocrine and paracrine fashion. It is postulated that differential post-translational processing of peptide precursors provide an additional level of control to these events. The project will use a combined proteomic and genomic approaches to study expression and processing of proproteins in the dense core secretory granule. Specific Aims will include: 1. Documentation of the proteome of the dense core secretory granule of pancreatic alpha and beta-cell lines with special emphasis on the relationship to the pattern of expression of genes that encode proprotein precursors and the cellular post-translational processing machinery. 2. Investigation of changes in the islet secretory granule proteome and gene expression during its embryonic development and post-natal growth. 3. Investigation of changes in gene expression in adult mice bearing conditional tissue-specific knock-outs of the NeuroD and Nkx 2.2 transcriptional factors. These analyses will expand both the list of candidate tissue morphogens involved in mammalian development and lead to the discovery of novel bioactive peptides within the sequences of known genes. The resources used in performing this study are available to other projects within the beta-cell consortium. The number of observations and hypothesis that the data will generate far exceeds our capacity to follow up more than a few interesting leads. Fortunately the data sets are easily stored in a standard format transferred electronically and will allow the information to be mined by other investigators and the diabetes research community at large.